I got my first Harbor Freight 6" digital Calipers in 1986 for $15....They do eat batteries, about 1 per 6 months....and the only other problem I have with them, is the battery cover tends to come off, and have to hunt for it a couple of times....Of course, I used them every day, doing CNC machining...and checking them with standards...they tend to be accurate within .002 of an inch.....
I would buy the 6 inch one, they have more uses than reloading, and a 4 inch limits the measurements....and are about the same price....I have seen them re-branded with different names, and almost twice the price for the same calipers....Guess they think people are stupid, and will buy the same thing, but with a different name on it!
Some of Harbor fieght tools are worth it, like this item, but be carefull with other tools that they sell....Most are not as good as USA made tools, but they do not charge much for them.....